Endoscopes are used for viewing ordinarily inaccessible sites such as internal organs of the human body. These devices are normally characterized by a flexible enlongated tube having a distal end for insertion into a passage leading to the object to be viewed and a proximal end at which an operator may view an image of the object. Images may be transmitted from the distal end to the proximal end of the tube by means of flexible bundles of translucent fibers, commonly called fiber optics. The use of such a fiber bundle allows the flexible tube of an endoscope to conform to the undulations of the passage leading to the area being viewed while forming at the proximal end and undistorted image of the object being viewed.
Normally, the distal end of the endoscope is inserted into the passage and advanced toward the site of the object to be viewed by grasping the emergent portion of the endoscope and simply pushing it inward. Where the passage is unusually tortuous or has a configuration which otherwise offers significant resistance to the endoscope traversing the passage, inward movement often cannot be achieved by pushing on the emergent portion of the flexible tube without causing severe pain to the patient. This pain is symptomatic of the force exerted on the walls of the passage by the flexible endoscope tube as it tends to bend laterally when the effort the operator exerts to advance the endoscope along the passage is opposed at the distal end.
Workers in the art have sought to alleviate the problem by various means. Efforts have been made to reduce the resistance to inward motion of the endoscope by enlarging the passage ahead of the distal end with the aid of compressed air which can be delivered to the distal end through a small hose built into the endoscope. This technique is difficult to use, for air pressure which is sufficient to enlarge the passage to a useful degree is generally great enough to at least cause pain and it may even be dangerous to the patient.
Various mechanical devices have been proposed for incorporation in an endoscope to aid its movement within the passage leading to the object to be viewed. Some of these devices have sought to guide an endoscope along a tortuous passage by means of cables connected to the distal end of the endoscope and controlled from the proximal end. Examples of such devices are disclosed in U.S. Pat. to Stickney, No. 2,961,495; Richards, No. 3,091,235; Bazell, No. 3,572,325 and Hall, No. 3,788,303.
It has also been proposed to move one component of an endoscope relative to another component by means of control cables extending from the proximal end to the distal end. For example, cables extending along the endoscope have also been used to move one or more lenses toward and away from the distal end of the bundle of fibers. Such a device is disclosed in the U.S. Pat. No. 3,090,378 to Sheldon et al. However, these techniques and devices of the prior art are of little or no aid in moving an endoscope inwardly along a tortuous passage to a site to be observed.